Power lift



N0v 17, 1953 F. w. WELLS ET A1.

POWER LIFT 3 Sheets-Sheet l Original Filed Feb. 27, 1942 Nov. 17, 1953 F. w. WELLS ET AL POWER LIFT 5 Sheets-Sheet 2 Original Filed Feb. 27, 1942 INVENTORS.

W/ v1 M B M 7. 5 d

Nov. 17, 1953 F. W. WELLS ETAL POWER LIFT 3 Sheets-Sheet 3 Original Filed Feb. 27, 1942 IN V EN TOR` Patented Nov. 17, 1953 POWER LIFT Frank W. Wells, Pasadena, Calif., and Joseph T.

Kulhavy.

Rock Island, Ill., assignors to J. I.

Case Company, Racine, Wis., a corporation of Wisconsin Original application February 27, 1942, Serial No.

432,670. Divided and this application October 4, 1947, Serial No. 777,994

The present invention relates to power lift apparatus and particularly to such apparatus as is adapted for application to tractors. 'I'his application is a division of a co-pending application, Serial No. 432,670, led February 27, 1942 and allowed April 9, 1947, now Patent Number 2,430,197.

An object of the invention is to generally improve the construction and operation of devices of this class. More particularly the invention relates to power lifts which are actuated by fluid pressure and a further object of the invention is to provide such a power lift operating upon a new land novel principle.

A further object of the invention is to provide expedients for the accomplishment o1' the novel objects.

Further objects are to provide such a power lift having Aa pump which operates only while power lifting operation is actually in progress and which is entirely stationary at other times.' such a power lift which while subject to manual control at any point in its cycle nevertheless will cease operation at a predetermined point regardless of the actuation of the manual control; such a power lift in which implements or objects lifted by the power lift may be held at any point in the lifting movement or in the lowering movement; and such a construction in which undue wear` on the parts is virtually eliminated.

A further object is to devise such a power lift providing a permanently located lifting element, but which is adapted to have one or more additional lifting elements at a distance from said location.

A further object is to provide such a power lift which may be actuated from any convenient power shaft normally in the tractor for another purpose.

Further objects and advantages of the invention will become apparent from a consideration of the following detailed description taken in connection with the accompanying drawings wherein a satisfactory embodiment of the invention is shown. However, it is to -be understood that the invention is not limited to the details disclosed :but includes all such variations and modifications as fall within the spirit of the invention as herein expressed. In the annexed drawings y traverses housing 5 and vreservoir 5, when desired, into a, ram cylinder :the tractor that one of the or objects connected with the lift.

4 Claims. (Cl. 103-23) Figure 1 is a vertical sectional view of an illustrative embodiment of the invention.

Fig. 2 is a sectional view taken on the line 2-2 oi' Fig. 1 with parts broken away.

Fig. 3 is an enlarged detail ci certain mechanism indicated in Fig. 1.

Fig. 4 is a similar view of another portion of Fig. 1.

Fig. 5 is a view of a part of the structure shown in Fig. 1, taken on the line 5 5 of Fig. 2, and showing a modified arrangement.

As seen in Fig. 1, the invention comprises a which may be bolted or tractor (not shown) in casing or housing 5 otherwise ilxed on a any convenient location to of. Housing 5 serves to enclose the mechanism of the power lift proper and also as a reservoir for fluid. A shaft 6 which may be, for example, a power take-off shaft extending from the tractor in any convenient or well-known location, is supported therein in anti-friction or other suitable bearings as 1. an oil seal 8 of suitable or well-known type being provided for the usual purposes, it being desirable to locate housing 5 at such a point on well-known externally projecting power shafts commonly provided will pass through the housing 5 tor serve as shaft 6. lShaft 6 actuates a generally designated as 9 which forces pump unit fluid from I 0 for accomplishing the usual purpose of a. power lift, the fluid returning to reservoir `5 through an outlet valve generally designated as II when it is desired to lower the implements In the event that excessive pressure is developed for any reason by the action of pump 9, this is relieved by a relief valve generally designated as I2 and control means generally designated as I3 operate to start and stop the actuation of pump 9 by shaft l6 and also to actuate outlet valve I I. control means I3 being adapted to automatically return to a neutral position whenever released, whereupon pumpl 9 stops and any implement connected with the power -lift remains in status quo.

Returning to a the construction, like member or more detailed description of housing 5 comprises a shellcasting having an open side become a part there-V closed by a cover plate I4 which may be removed for access to the interior.

Most of the operative parts are supported on and carried by housing 5. For example, pump 9, in the present instance comprises plungers I5 and I6, Fig. 2, reciprocable in suitable bores in housing 5, in the present instance in a substantially horizontal position. The bores I5a and I6a for plungers I5 and I6 may be formed through suitable openings in housing 5 closed by plugs I1 and t8. Since plungers I5 and I6 are identical in function and construction, only one will be described in detail.

As seen in Fig. l, plunger I6 has pivotally connected thereto as by a pin I3, a link 20 in turn pivotally connected as by apin v2i with an arm 22 of a bell crank generally designated as 23. Bell crank 23 is journaled on supported in housing 5 in any suitable manner and has an arm 25 carrying va roller 26 which may engage a cam element, eccentric, or other reciprocating or pulsating mechanism 21 xed with above mentioned shaft 6. Other suitable or well-known cam plated as equivalent to roller 26 and the invention is not Vto be taken as limited to the use-of a roller, or 'in fact in any manner -except as dened inthe claims. Bell crank 23 also rhas an arm 21a to which is .connected in the present instance a spring 23 by an anchorage 29 of a character such that spring 28 may'exert a 'downward or `an yupward force against arm 21a at will. A similar anchorage 30 is provided for the opposite end fof spring 28 to connect the same .to above mentioned -control :means I3, Vthe function of which will :be more easily understood after the :hydraulic circuit is ldescribed. As shown :in Fig. 1, spring 12B is in compression and tends to rotate :bell crank 23 in a counter-clockwise direction. Rotation of shaft 6, as will be apparent, repeatedly rocks bell `crank 23 in .a clockwise direction against the compression of spring 23, the expansion 'of the spring .causing the return Vmovement 'of bell crank 23 so that roller 26 will Afollow cam member 21. This causes reciprocating or pumping movement of plunger I6 as will be apparent.

Anchorage 30 is yfined with a Aplate 3I which is iixedly connected with a rod 32 forming a part of control `means 'I3 :and extending upwardly through .a guide portion 33 iin housing 5. Rod 32 in the present instance has a spring 34 compressed between housing 5 and an abutment 3S, fixed relatively tothe rod by a pin or other suitable means 38. In the position of the parts shown, spring 34 has been overcome by the clockwise rotation of a hand lever generally designated as 31 fulcrumed at 38 on an anchorage 33 supported on the tractor at any desired or convenient point. Lever 31 has an arm 40 pivotally connected by a link or other appropriate means Il with above mentioned rod 32. Spring 3l is so proportioned as to raise rod 32 upon release of lever 31, plate 3| sliding upwardly on a guide rod 42, fixed within housing 6, to dotted position A at which point spring 23 is no longer in compression but is in tension. Plunger I6 upon completion of a stroke by action of cam 21 on bell crank 23, will take a position at its innermost point in bore I6a and will remain sta.- tionary and pump no more fluid.

Plunger I5 is actuated in the present instance in an identically similar manner from a cam 21h actuating a bell crank 23a. identical with bell crank 23, and the parts being returned by a shaft. v24

follower means is echtem- 41 by means of a-spring 40 a spring 23a connected to an arm 21c on bell crank 23a. Plunger I5, of course, also goes out of operation as above mentioned, and the action of pump 9 ceases.

The innermost position will be such that cam 21 may lightly contact roller 26 upon each revolution of shaft 6, resulting in a slight ticking sound and possibly unnecessary wear on the parts. This may be avoided by any means fallowing the escape oi fluid from bores I5a and ISa, in the present instance valve unseating devices generally designated as 43-43a.

For a full understanding of this expedient, V'it 'is necessary to describe the fluid passageways at this point. A `Abore 44 extends from above mentioned cylinder bore I6a into a bore 45 constituting a pump valve chamber. Bore 45 has therein an intake valve in the present instance in the .form of a. ball 46 seated against a shoulder engaged between the ball and an abutment 43 o! any suitable type. Shoulder 41 is dened between above mentioned bore 45 and a bore 50 forming the intake port for valve 46. An outlet or exhaust valve 5I is seated against a shoulder 62 defined between above .mentioned bore 43 and 'a bore 63. Ball 5I is maintained against Aits seat by a spring 54 conmressed between 4ball 6I and a plug 55 threaded or otherwise secured in bore 5I.

:It will be understood that a precisely similar arrangement is associated with above mentioned plunger I5, an inlet valve 46a, Fig. 5, being seated against a Vshoulder' 41a formed between a bore `45a and a bore 53a, and an outlet valve 51a being seated against a shoulder 52a lformed between vbore 46a `and a bore 53a, constituting an outlet chamber for 'pump cylinder I5a. Outlet chamber 53a correspondingto bore 63 is communicated or Aconnecteiil with bore 53 by a bore 56. A two-cylinder single acting pump is therefore provided by the utilization of connecting passageways, drilledm otherwise suitably formed in a portion ofthe wall of housing 5.

In the present instance leading from here 5I is a bore '61. `A ynon-retin'n or check-valve 5S is Vseated on a-shouido'r 53 defined between above mentioned bore 51 and a bore 60 leading to the exterior of housing I and the end of which is closed vin the present instance by a removable plug lor the like '6I. Valve 6I is seated by means of a spring i2 compre'ed between the valve and an abutment 6l of any suitable type.

.A bore 64 leads upwardly from bore 3u into above mentioned ram cylinder I6 and in the present 4instance is lthreaded at 65 to provide for blocking of the bore 66 opposite bore 34 is closed by a plug 61 upon the removal of which access may be had to threaded portion 65 of bore 64.

It will now be apparent that reciprocating movement of plunger I! will cause pumping of uid inwardly through bore 63 past valve 46 and expelling of fluid past valves 5I and 58 into bore GII and thence .through bore I4 into ram cylinder I3.

In the present illustrative embodiment, a bore 63 leads upwardly out of above mentioned bore 6B and defines a shoulder 63 between itself and a bore 16. An outlet valve 1I is seated against shoulder v69 by a spring I2 encompassing a pin 13 or extension of an adjusting screw 14 threaded into housing 5. Valve 1I accordingly normally remains seated on 'shoulder 63 and prevents estaken by plunger It cape of fluid from bores 63 and 60. Ball 1I, howbore when desired, and aA ever, may be unseated by a iinger as will be presently apparent.

Relief valve |2 operates from bore 68 as follows: A bore 16 extends from bore 68 defining a shoulder 11 between itself and a bore 18 extending to the exterior of housing 5. A ball valve 19 is seated against shoulder 11 by a fitting 80, a spring di, and a screw 82, in the present instance threaded in housing 5. In this manner a relatively high unit pressure may be secured against a valve having a relatively small area exposed to fluid pressure. A bore 83 leads from bore 18 into the interior of housing or reservoir 5. Thus in the event excessive pressure is developed by pump 9, ball 'i9 will be forced away from shoulder 11 and uid will escape through bores 16 and 83 and return to reservoir 5. In the present instance, spring 8| is so compressed that this will occur normally when the desired limit of power lift movement is reached until such time as lever 31 is released.

A box like element 83a is preferably disposed over elements 43 and 43a, being iixed to housing 5 :flange 53h clamped by a screw or the like 89e, and having its walls made of screen material.

By virtue of the fact that fluid is pumped only during the time that lifting is actually being accomplished, there is no difliculty from heating of the iuid, and as a result, pump 9 and cylinder lil may be made substantially larger in volumetric capacity than would be the case with any kind of a continuously pumping hydraulic circuit. As a result the present lift Will perform a given lifting task with a correspondingly smaller fluid pressure than power lifts of known type. The pressure at which relief valve |2 is set to open need not be greatly in excess of the maximum pressure necessary to perform the work of the lift, and in no case is it suiiiciently high to cause any undue stress in the parts. Thus, while valve i2 operates as an emergency relief valve,

it is not exclusively an emergency valve, and

actually operates for a short time each time the lift is operated. rhis tends to keep it in good operating condition so that it will not fail in case an emergency does arise. Furthermore, owing to the relatively low working pressure, ne undue heatingof the uid will occur even if the relief valve operates longer than normal, as in the case of an inexperienced operators holding lever 51 in the working position after the power lift has completed its lifting stroke.

Screw 82 may be adjusted to arrive at the de degree of compression of spring 8|. Also screw 14 may be adjusted to provide for a desired amount of clearance between pin 13 and valve 1| so that the degree of opening of valve 1| may be positively controlled. In this way the return or dropping of implements or other objects acted up n by the power lift may be deiinitely predete' dined, as will appear.

eturning to unseating device 43, as more particularly shown in Fig. 3, the device comprises a shell S4 having a large bore 85 within which is reciprocable a guide portion 8B of an unseating pin S1. Inlet bores Slm-81a provide for entrance ci fluid into the shell and accordingly into bore Guide portion 88 is forced upwardly by a bring 68 against a stop 89 of any suitable type, the present instance anchored in a slot or slots 99 in shell S9. Guide 96 has an Iabutment 9| extending upwardly for actuation by a iinger 92. lFinger 92 presses downwardly upon abutment 9| forcing the parts to the dotted position shown whereupon valve 46 is forced away from shoulder 41 thereby relieving the pressure in pump cylinder bore |6a, as will be apparent from Fig. 1.

Finger 92 has a counterpart 93, the two being united by a portion 94 connected with a lever 95. Lever 95 is fulcrumed on a pin 96 carried on a support 91 threaded or otherwise anchored in housing 5 as at 98.

Lever 95 is actuated by a tension spring 99 connected between lever 95 and above mentioned plate 3| in any suitable manner. As will now be apparent,'when lever 31 is released, spring 34 will expand, raising rod 32 and causing a tension in spring 28, and also a tension in spring 99. This will rock lever 95 and ngers 92 and 93 in a counter-clockwise direction as seen in Fig. 1, thereby pushing down unseating pin 81 and its companion pin 81b, Fig. 5, associated with plunger I5. The several springs 34, 28, 28a, 99, 88, 88a, 48, and 48a are so proportioned that springs 28, 28a and 99 will be tensioned and springs 88, 88a, 43, and 48a will be compressed by the expansion of spring 34 when lever 31 is released, and plate 3| takes position A. Pressure in the pump cylinders will be released and the tension in spring 28 will produce the extreme inward position of plunger I8, the same thing happening in plunger 5 as will be understood. This' removes bell cranks movement of cams 23 and 23a from the path of 21 and 21b and avoids'any movement of the pump parts from the rotation of shaft 6.

Ram cylinder l0 has a piston therein generally designated as |00 having a rod |0| extending upwardly through a suitable oil retainer of any well-known type |02. A head |03 is fixed to rod |01 and extends to one side where it is fixed with a guide rod |04, slidable in a guide portion |05 in the present instance forming part of housing 5. In this manner piston E00 is denitely guided independently of cylinder l0 so that any side thrust reaction occasioned by implements connected to be lifted rod |94 rather than the walls of cylinder |0. Undue wear of the cylinder is thereby eliminated.

To minimize such side thrust, a ccnnection to elements to be lifted provided in the present instance in the form of a rocli shaft i journaled in a suitable bearing |91 fixed with the tractor. Any well-known connection from rock shaft |96 to the various implements which it is desired to lift may be provided as will readily be under stood by one skilled in the art. Rock shaft has a bifurcated. arm |93 extending to a region above piston rod lll-I at which point it is pivotally connected with a thrust block |99 by a pin or the like l0. Thrust block |99 is pivctally connected as by a pin with a biiurcated or suitable guide arm |52 pivoted at |13 in the present instance to above mentioned bearing i 0?. Thrust block |09 has a face Hd preferably at right angles to piston rod 59| and head 53 .is provided with an anti-friction. abutment, for example, a roller l5 in contact with face l M.

In the present arrangement, pivots ii IH are disposed in a plane parallel to rod I... Rock shaft |06 and pivot H9 are also disposed in a plane parallel to shaft lil, arm and guide arm H2 being of equal length. Consequently, during swinging movement of arm |08 and guide arm H2, block H39 will in all positions remain parallel to rod HH. Therefore, since face ||4 is at substantially right angles to rod lili,

the reaction on rod 9| will always be axial to the or the like is taken by guide rod and no side thrust will be developed by the rod |01 against block |00. Any side thrust developed by friction roller I5 is taken up by guide rod |04. Other arrangements which will insure that face ||4 will remain perpendicular to rod are contemplated as within the scope of the invention.

It will now be apparent that clockwise movement of lever 31 will compress springs 34 and 20 and relax springs 90, 08, 48, etc., therein1 releasing intake valves 46 and 46a to close, and rctracting plungers` |4 and |6. If shaft 6 is rotating, plungers I5 and |6 will be reciprocated by cams 21 and 21h and fluid will be pumped through passageway 60 into cylinder l0. This will raise piston |00 and rod |0| and block |09, rocking arm |08 and a rock shaft |05 in a counterclockwise direction. This action will continue as long as lever 31 is held in the above position, but will stop immediately if lever 31 is released, piston |80 being held in whatever pcsition it has reached by a closing of non-return valve 60. If lever 31 is not released, but continues to be held, pump 0 will continue to run until piston |00 reaches the limit of its movement whereupon pressure in the several passageways will rise to a point to force valve 10 to open against spring 8|, whereupon the fluid pumped. will be returned through bore 83 to reservoir 5. The operator holds lever` 31 until this condition occurs, which ordinarily takes only a few seconds, and no complications such as a cyclic clutch trip valve, or other expedients are necessary. [iis as above suggested, if for any reason operator does not desire to lift the implements to their full extent, he may release lever- 3'! at any time during the upward movement, rfc upon the parts will remain in the position attained.

Lever 31 also functions to allow the implements to drop as follows:

Above mentioned guide rod 42 has s slide block ||0 adjacent the upper end thereof, connected by a link H1 pivotcd to the block at H3, and connected with a lever generally designated as H0. Lever ||9 is fulcrumed at |20 on a standard or support |21, fixed in any suitable manner with housing 5. Lever ||9 has an arm |22 connected with link ||1 and also an arm |23 in the present instance bending about cylinder I0. Arm |23 is preferably, although not necessarily, bifurcated at |24 and has a pin |25 pivotally ccnnected to a block |26, carrying above mentioned finger 15.

It will 4be noted that in position A of plate 3|, slide block ||6 is unaffected. However,

counter-clockwise movement of lever 31 beyond the position attained by merely releasing the lever will move plate 3| to position B." This is permitted by further extension of springs 28, 28a and 99. Plate 3| in position B raises slide block ||6 and rocks lever ||9 in a counter-clockwise direction by means of link I |1. This pushes down on finger and unseats ball valve 14 to the extent determined by the position of lever 31, or permitted by pin 13. Fluid in cylinder I0 therefore escapes from cylinder I0 through bores 64, 60, 60 and 10, allowing piston |00 to fall at the rate determined by the adjustment of screw 14, which as above noted, governs the degree of opening of valve 1| by pin 13.

As in the case of the raising movement of piston |00 and the attached parts, this lowering movement may be' arrested at any desired point by merely releasing lever 31. Plate 3| immediately returns to position A" closing valve 1|.

Since pump 9 is inoperative, in this position, piston |00 does not move either way.

Returning to a further description of certain mechanical details, piston |00, as more particularly shown in Fig. 4, is assembled in a stem portion |21, extending downwardly from above mentioned rod |0| and defining a shoulder |20. A plate |29 of suitable material, such for example as soft metal, rests against shoulder |20 and guides the piston within the wall of cylinder ||0 and is locked in place against shoulder |20 in the present instance by a lock nut |30, nut |30 being threaded on stem |21, and provided with openings |3| and |32. for reception of a spanner or other tool for adjusting it. Disposed about lock nut |30 is a hydraulic packing assembly generally designated as |33 and preferably, although not necessarily, of the type known in the trade as Chevron packing. A lock nut |34 is also threaded on stem |21 for compressing packing |33 and has openings |35 and |36 to be engaged by a Spanner or other suitable instrument for tightening the nut. Nut |34 exerts its pressure against packing |33 through a washer |31 of spring metal or the like and having an offset configuration, such that it is resiliently yieldable under pressure of nut |34. Therefore, washer |31 will follow up any shrinkage or normal weer of packing |33 so that it will remain tight during long periods of operation without adjustment.

Cylinder I0 may be secured in housing 0 in any suitable or desired manner, in the present instance the cylinder being seated against a gasket |38 in a counter-bore |30 by means of va nut |40 threaded in a boss |4| in housing 5. Nut |40 carries above mentioned oil retainer |02 and preferably has a. bore |42 for receiving the upper end of cylinder |0. Cylinder I0 has a notch or opening |43 communicating with a clearance |44 provided in bore |42 for communication of the space -above piston |00 with the interior of housing 5.

This relieves any pressure or partial vacuum which might otherwise form above piston |00.

The modication shown in Fig. 5 is designed to be used for such purposes as would not be conveniently served by the location of ram cylinder I0 and piston rod |0| in or on housing 5, the pump and control means disclosed serving as l part of its function to control a. similar ram cylinder at a distance from said housing 5. Examples of such use might be where a snow plow, or the like, was mounted in an overhanging position in front of the tractor. Such a plow could be controlled by lever 01 as follows. Plug 6|, Fig. 1, is removed and in its place is inserted a fitting or portion |45, Fig. 5, of a. flexible or suitable conduit |46 which leads to the desired point of cperation. Conduit |46 is connected preferably at |41 to a ram cylinder generally designated al |48 which may be constructed along the lines of above mentioned ram cylinders I0 and |00. although any other suitable or well-known construction of ram is considered as within the scope of the invention. In the present instance mm |48 is provided with an anchorage |49, a piston rod |50 and a clevis or other suitable connecting means |5|. Cylinder |48 is anchored by means of portion |49 on any convenient part of the structure and clevis |5| is connected with a portion of the structure where it is desired to have movement relative to the part to which |40 is fastened. Actuation oi' lever |31 will then cause actuation of piston rod |50 relatively to cylinder |40 in the manner above described in the case of piston rod I0|, and the attached imple- 9 ment or parts will be controlled in the same manner. Y

In fact cylinder |48 need not necessarily be located on the tractor within the present invention, but might be for example on an implement drawn by the tractor and which had a part which was desired to be raised and lowered or otherwise adjusted by the operator on the tractor.

When cylinder |48 is in use, if it is desired that cylinder shall become inoperative, plug 61 may be removed and a plug |52 may b e linserted in above mentioned threaded portion 65, whereupon cylinder I0 will be blocked from passageway B0. With plug 61 replaced, cylinder |48 and piston rod |50 alone will respond to the control of lever 3'|.

It is thought the operation of the above described construction will be clearly apparent from the foregoing, it being noted that pump 9 operates only while lifting is actually in progress; that implements or other parts subject to the control or" the device may be locked at any stage in the movement in either direction without other attention than to release the control levers; that no damaging side thrust is exerted on piston rod im to cause undue wear of cylinder I0 and that there is no danger of accidents to the mechanism in the event that movement is blocked for any reason or that pump 9 is allowed to operate too long through inattention or otherwise.

As to actual manipulation of the mechanism, no attention need be paid to the unit until it is desired, for example, to raise an implement carried by the tractor, all the power lift parts being completely at rest and subject to no wear (assuming shaft 6 to be in the tractor for another purpose, such as a power take-01T or a belt pulley shaft). When it is desired to lift an implement, lever 31 is grasped and raised or rotated clockwise as seen in Fig. 1. Pump 9 immediately goes into action and extends ram piston rod ||l|, thus lifting the implement through appropriate connections from rock shaft 6. No particular attention need be paid this operation, since when the implement has reached its uppermost position, further movement of piston |00 will be blocked by plug |49 or by implements or other connected load, and fluid being pumped will escape through valve l2. The operator releases lever 31 when the implement is obviously at its uppermost position, when it is held there by the accumulation of fluid under piston |90. If the operator does not wish the implement to move to its uppermost position, he may release lever 31 at any time during the upward travel when the implement will be held in the new position. This is so because uid cannot return to pump 9 because of non-return valve 58. Of course, the iluid could not get back to the pump cylinder because of outlet valves and 5|a, but non-return valve 53 makes it all the more certain that the iluid will be positively retained and prevent the implements from gradually returning to lowered position.

When it is desired to lower the implement, the operator presses down on lever 31, or rotates it counter-clockwise, as seen in Fig. 1, where` upon outlet valve 1| is opened, allowing escape of fluid from cylinder I9, and dropping of the implement.

is above noted, this movement may also be arrested at any desired point by releasing lever if it is not desired to lower the implement to its full extent. Both of these conditions also apply to cylinder |48, in Fig. 5.

As above noted, the rate that theimplement drops, may be regulated by adjusting screw` 14, to determine the clearance between valve 1| and the end of pin 13.

lThe above being ka complete description of an illustrative embodiment of the invention, what is claimed as new and desired to be secured by Letters Patent of the UnitedStates is:

1. In a power lift construction, means p'roviding a fluid passageway, a valve element seated in said passagewayifor,controlling the iiow of duid therethrough, a' shell having a bore communicating with said passageway and co-axial therewith, an unseating element comprising a guide portion slidable in said bore, and having an unseating pin extending into said passageway and terminating adjacent said valve element, means providing for passage of fluid past said guide portion, an abutment on said guide portion protruding from said bore, resilient means in said bore contacting said guide portion and urging said pin in a direction away from said valve element, means to prevent removal of said unseating element from said bore, a perforate enclosure surrounding said shell and provided with an aperture for said abutment in the perforate portion thereof, and means outside said enclosure to depress said abutment to effect unseating of said valve by said unseating pin.

2. In a power lift construction, means providing a iiuid passageway, a valve element seated in said passageway for controlling the iiow oi iluid therethrough, a shell having a bore communicating with said passageway, an unseating element comprising a, guide portion sliolable in said here, and having an unseating pin extending into passageway and terminating adjacent said valve element, an abutment on said guide portion protruding from said bore, resilient means in said bore, contacting said guide por tion and urging said pin in a direction away from said valve element, means to prevent inadvertent removal of said unseating element from said bore, a screen surrounding said shell and said screen being provided with an aperture for said abutment and means exteriorly of said screen to depress said unseating element to eifect unseating of said valve by said unseating pin.

3. In a power lift construction, means providing a fluid passageway, a valve element seated in said passageway for controlling the flow of fluid therethrough, a shell having a bore communicating with said passageway, an unseating pin extending into said passageway, an abutment on said guide portion protruding from said bore, resilient means in said bore, contacting said guide portion and urging said pin in a direction away from said valve element, means to prevent removal of said unseating element from said bore, a perforate enclosure surrounding said shell and provided with an aperture for said abutment in the perforate portion thereof, and means to depress said abutment to eiTect unseating of said valve by said unseating pin.

4. In a power lift construction, means providing a uid passageway, a valve element seated in said passageway for controlling the iiow of iluid therethrough, a shell having a bore communicating with said passageway, an unseating element comprising a guide portion slidable in said bore, and having an unseating pin extending into said passageway and terminating adjacent said valve element, an abutment on said guide portion proy truding from said bore, resilient means in said :www

-ll pqre. contadina' ald urzin um 1n a aired-.in away from sazia yaxve ent. @w15 Vt0 rtin S `e1e meh't 'in said bore. a Mont enlqsur'e surrounding said shell and "provided w'th an aperur' fr said abutmenbin the .prforate xjefl. and means t'o deires said abutment 'to UNrrEDsTATEsPA'rENTs Nimm Rame DIM MeKn, Jr. Apr. 9. 190'! k Oct. B, 19,1 Au!- 11. 1908 Aus. 11 1914 Blumen Dec. 22. 1925 Jorgensen Feb. 2. 1926 Aug. 27, m0 Kravtis Jan. 13, 1942 

